Immersed ram hydraulic hammer

ABSTRACT

A hydraulic hammer having a ram reciprocally moveable in a casing filled with hydraulic fluid. An axial bore in the ram maintains the end of the casing in open fluid communication. An anvil is impacted within the casing by the ram and high energy forces are transmitted out via a stem of the anvil.

United States Patent 1 Gendron et al.

[451 May 6,1975

[ IMMERSED RAM HYDRAULIC HAMMER [75] Inventors: George J. Gendron; Henry A.

Nelson Holland, both of Houston, Tex.

[73] Assignee: Raymond International Inc.,

Houston, Tex.

22 Filed: Aug. 27, 1973 2| App1.No.:391,569

[52] US. Cl. 173/131; 92/169; 92/181 F;

[51] Int. Cl E02d 7/10 [58] Field of Search 173/127, 133, 128, 134,

[56] References Cited UNITED STATES PATENTS 1,005,770 10/1911 Clark 173/127 X 1,257,762 211918 Sturkevant.............t............ 173/127 3,146,835 9/1964 Hornstein 173/103 X 3,332,503 7/1967 Klebanov 173/134 3,646,598 2/1972 Chelminskii. 173/1 X 3,735,820 5/1973 Curington.................. 173/133 X Primary Examiner-Frank L. Abbott Assistant ExaminerWi1liam F. Pate, 111

Attorney, Agent, or Firm-Fitzpatrick, Cella, Harper & Scinto [57] ABSTRACT A hydraulic hammer having a ram reciprocally moveable in a casing filled with hydraulic fluid. An axial bore in the ram maintains the end of the casing in open fluid communication. An anvil is impacted within the casing by the ram and high energy forces are transmitted out via a stem of the anvil.

21 Claims, 11 Drawing Figur es PHENTH HAY SHEET 2 OF 8 1 IMMERSED RAM HYDRAULIC HAMMER This invention relates to hammering systems and more particularly it concerns novel means for applying heavy hammer blows to piles and other elements requiring repetitive high impact forces.

The present invention is particularly useful in the driving of piles and the like from submerged locations into a sea bed. The operation of pile driving equipment at substantial underwater depths presents a number of problems due to the pressures and damping effects incurred. Where hydraulic hammers using hydraulically driven rams are employed, special seals are needed to isolate the hydraulic ram driving mechanism from intrusion of the surrounding high pressure water. Also, the damping effects of the surrounding water hinder the buildup of high velocity in the ram before it strikes the pile or an anvil which transmits ram impacts to the pile.

The present invention alleviates these problems of the prior art, and permits the driving of piles in submerged locations in an efficient and reliable manner.

According to the present invention there is provided a hydraulically actuated pile driving hammer having a ram which is enclosed for movement in a liquid filled casing. The liquid in the casing is preferably maintained at or near the pressure of the surrounding water. An anvil extends into the casing where one end is struck by the ram during its movement. The other end of the anvil is outside the casing and transmits the hammer blows to the pile being driven. A seal is provided where the anvil enters the casing. Because the ram strikes the anvil inside the casing no casing seal is needed for the ram; and since the anvil moves much less than the ram only slight wear is produced on the anvil seals. Further, the pressure inside the casing, being close to that of the surrounding water, minimizes stresses on the anvil seal.

In order to ensure free movement of the hydraulically immersed ram of the present invention, means are provided to maintain free and open fluid communication between the spaces within the casing which are displaced by the ends of the ram. In the preferred embodiment this means comprises an axial passageway extending through the center of the ram from one end to the other.

The present invention, in one aspect, provides hydraulic ram actuator means within the casing in which the ram is immersed. This hydraulic actuator means includes at least one variable size pressure chamber having different walls fixed, respectively, to the casing and to the ram, and means for controlling the flow of fluid at different pressures into and out from the chamber. Pressure seal means are provided to isolate the pressure chamber from the interior of the casing. While this pressure seal means must accommodate the ram movements, any leakage across it merely passes into or back from the casing, and no loss of fluid or contamination results.

In a preferred embodiment of the invention the hydraulic actuator means is built into the ram and casing. This arrangement includes a casing having adjacent, axially aligned bores of different diameter and a ram also having axially aligned sections which fit closely, respectively. into the casing bores. The interior of the casing is filled with hydraulic fluid maintained at a constant pressure and fluid is alternately forced into and withdrawn from the space bordered by the smaller section of the ram and the larger bore of the casing.

Also according to the present invention, special pressure actuated means are provided to obtain switching of the hydraulic actuating means. This special pressure actuated means include pilot passageways extending through the casing walls and communicating with a side of the ram moving in the casing. The ram interior communicates with the constant pressure fluid at the ends of the ram; and ram pilot passages connect the ram interior with the ram pilot ports strategically located along the ram. When the ram reaches predetermined positions, the ram pilot ports become aligned with the pilot passageways in the casing and the pressure of the constant pressure fluid in the casing is communicated via the passageways to a valve actuating system.

There has thus been outlined rather broadly the more important features of the invention in order that the de tailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described more fully hereinafter. Those skilled in the art will appreciate that the conception on which this disclosure is based may readily be utilized as the basis of the designing of other structures for carrying out the purposes of this invention. It is important, therefore, that this disclosure be regarded as including such equivalent constructions as do not depart from the spirit and scope of the invention.

A preferred embodiment of the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawings, forming a part of the specification, wherein:

FIG. 1 is a side elevational view of a hydraulic hammer in which the present invention is embodied;

FIG. 2 is an enlarged section view of the hammer taken along line 3-3 of FIG. 1;

FIG. 3 is an enlarged section view taken along line 3-3 of FIG. 1;

FlG. 4 is an enlarged section view taken along line 4--4 of FIG. 1;

HQ 5 is a section view, broken apart, taken along line 5-5 of FIG. 2;

FlG. 6 is a hydraulic schematic illustrating hydraulic control of the hammer of FIGS. 1-5; and

FIG. 7-1 1 are elevational sectional views illustrating, respectively. the successive stages of ram movement in the hammer of FIGS. 1-5.

The hydraulic hammer assembly shown in FIG. I includes a casing assembly 18, made up of an upper casing section 20, a central casing section 22, and a lower casing section 24 in stacked arrangement. The casing sections are held together by means of tie rods 26 which extend outside the casing assembly along it length. The tie rods 26 pass through openings in flanges 28 which project laterally from the casing sections near their upper and lower edges. Lower end nuts 30 are provided on the bottom of the tie rods 26 and upper end nuts 32 are provided on the upper end of the tie rods 26 to squeeze the sections together. The upper ends of the tie rods pass through tubular spacers 33 and through associated openings in a top plate 34. Additional tie rods 25 extend between the various casing sections. The top plate 34 is provided with a sheave 36 for allowing the hydraulic hammer assembly to be supported by cables (not shown).

The tubular spacers 33 provide an opening 38 between the top of the upper casing section and the top plate 34. This opening allows room for the mounting on top of the upper casing section 20 of a main switching valve 40, an upstroke pilot valve 42, a downstroke pilot valve 44 and a latching pilot valve 46. These valves are connected to each other and to various elements within the hydraulic hammer assembly via a network of passageways to be described hereinafter.

A plurality of accumulators 48 and 49 are mounted on the upper casing section 20 near the various valves 40, 42, and 46. The accumulators serve to maintain pressures in the system by accomodating various fluid flows during operation of the system; and they are connected by means of various hydraulic lines or passageways (as described hereinafter), to the valves and to the interior of the casing assembly 18.

An anvil housing 50 is secured to the bottom of the lower casing section 24 and a cap block 52 extends down from the anvil housing 50. The cap block 52 is configured to accomodate the top of a pile or other elements to be driven; and it serves to transmits the driving forces developed inside the hammer assembly to the pile or other element.

The internal construction of the hydraulic hammer assembly is best seen in the enlarged section view of FIGS. 2-5. As shown in FIG. 5, the upper, central and lower casing sections 20, 22 and 24 are provided with axially aligned bores 54, S6 and 58 respectively. A massive cylindrical ram 60 is fitted closely inside the casing bores 54, 56, and 58. The ram 60 has an upper small diameter region 60a, a central, large diameter section driving and control region 60b and a lower, intermediate diameter region 601'. The large diameter central driving and control region 60b is much shorter in length than the upper and lower regions 60a and 60c. The overall length of the ram 60 is such as to allow it to move longitudinally within the casing bores 54, 56 and 58 while the intermediate driving and control region 60b moves between the upper and lower ends of the intermediate bore 56.

The driving and control section 60b of the ram 60 is formed with upper and lower pairs of peripheral grooves 62 and 63 into which ram sealing rings 64 and 65 are fitted. These sealing rings, which constitute the largest diameter portion of the ram 60, press against the inner wall of the intermediate casing bore 56.

The small diameter upper ram section 660 is supported within the upper casing bore 54 by means of an upper hydrostatic bearing 66. This bearing is fitted into the upper casing bore 54 and is supplied via an upper beating supply passageway 68, with a continuous flow of pressurized fluid from an external source (not shown) to maintain the upper end of the ram 60 centrally positioned within the upper casing bore 54, while presenting a minimum of frictional restraint to longitu' dinal movements of the ram. The lower ram section 600, extends into the lower casing bore 58 and is supported therein by means of a lower hydrostatic bearing 70 which similarly receives a flow of pressurized fluid via a lower bearing supply passageway 72 in the lower casing section 24.

An upper seal assembly 74, which comprises a plurality of ring like seals separated by spacers, is positioned near the bottom of the upper casing bore 54 and is separated from the upper hydrostatic bearing 66 by means of an elongated upper bushing 76 extending along the bore 54. The upper seal assembly 74, presses against the periphery of the small diameter upper ram section 60a. Similarly, a lower seal assembly 78 is secured inside the lower casing bore 58 near its upper end; and this lower ram seal assembly is maintained in position spaced apart longitudinally from the lower hydrostatic bearing by means of an elongated tubular lower bushing 80.

It will be appreciated that the large diameter driving and control region 60b of the ram 60 divides the larger diameter intermediate casing bore 56 into upper and lower pressure chambers 82 and 84. The upper pressure chamber 82 is formed between the small diameter upper ram section 600, the upper ram sealing rings 64, the larger diameter intermediate casing bore 56 and the upper seal assembly 74. Similarly, the lower pressure chamber 84 is formed between the intermediate diameter lower ram section 600, the lower ram sealing rings 65, the larger diameter intermediate casing bore 56 and the lower seal assembly 78. The pressure chambers 82 and 84 vary in size inversely as the ram 60 moves up and down. That is, as the ram 60 moves upwardly and the sealing rings 64 approach the upper ram seal assembly 74 the upper pressure chamber 82 becomes shortened. At the same time, the lower pressure chamber 84 becomes lengthened as the ram sealing rings 65 move upwardly and away from the lower seal assembly 78. Further, because the upper ram section 600 is of a smaller diameter than the lower ram section 60c, the upper pressure chamber 82 is provided with greater area in the direction of ram movement than the lower pressure chamber 84. Consequently when the two pressure chambers 82 and 84 are subjected to the same pressure, a net downward thrust is produced on the ram, causing it to move in a downward direction.

As can be seen in FIG. 5. the accumulators 48 are each formed with a bore 86 into which is fitted a floating piston 88. Pressurized air or other elastic substance is provided in the lower portion of the bore 86 underneath the piston 88, and the bottom of the bore 86 is closed by means of a cap 90. The portion of the bore 86 above the floating piston 88 is filled with hydraulic fluid; and this is communicated via passageways 92 to various portions of the hydraulic system as will be described hereinafter. It will be appreciated that the accumulators 48 serve to accomodate flows of fluid into and out of the portion of the bore 86 above the floating piston 88', and they further serve to maintain fluid at a substantially constant pressure as the piston 88 moves downwardly against the resilient action of air or other substance provided therein.

As can be seen in H65. 2 and 5, the ram 60 is provided with an axial bore 94 extending completely through the ram from one end to the other. This axial bore provides free and open liquid communication between the upper end of the upper casing bore 54 and the lower end of the lower casing bore 58. Thus, as the ram moves up and down within the bores, fluid displaced in front of the moving ram is free to pass through the axial bore 94 to the region evacuated by the opposite end of the ram. Transverse pilot passageways 96 extend from the axial bore 94 to a recess 98 fomled about the periphery of the intermediate driving and control section 60b of the ram between the upper and lower sealing rings 64 and 65. As the intermediate driving and control section 60b of the ram moves up and dbwn within the intermediate casing bore 56, the

tion 22. As will be explained more fully hereinafter, this serves to produce actuation of the various valves which control switching of ram movement.

As shown in FIG. 5, the anvil housing 50 is fitted into the lower end of the lower casing section 24 and is secured thereto by any suitable means such as welding. The anvil housing 50 is essentially of tubular configuration and is formed with an upper counterbore I06 into which a band shaped upper anvil housing I08 is secured. A lower anvil bearing I10 of smaller diameter is secured to a lower smaller diameter portion of the anvil housing 50. A ring seal II2 is positioned adjacent the lower anvil bearing I10, and a lock ring 113 is threaded into the anvil housing to hold the ring seal 112 and lower anvil bearing IIO in place.

A mushroom shaped anvil I14 having an upper enlarged head II6 and a lower, smaller diameter stem II8 is mounted inside the anvil housing 50 with the head 116 positioned in the counterbore 106 and the stem II8 fitted to slide through the lower anvil bearing 110 and the ring seal II2. As shown, the anvil 114 is in axial alignment with the ram 60 in its path of movement so that as the ram 60 moves downwardly in the casing it strikes the anvil to deliver a hammer blow to the anvil within the casing. The head 116 of the anvil is formed with a peripheral band-like sliding section I which fits closely inside and slides along the upper anvil bearing I08. The head II6 of the anvil 114 is also formed with a large diameter axial bore I22; and radial passageways I24 provide fluid communication between the region above the anvil I I6 and the region between the sliding section 120 and the lower anvil bearing IIO. This permits free movement of the anvil up and down inside the anvil housing 50.

The anvil head I16, as shown is of convex configuration; and this corresponds to a concave indentation 125 in the lower end of the ram 60. This insures proper centering of the ram and anvil during impact and it also maintains a proper distribution of fluid over the contacting ram and anvil surfaces so as to minimize noise and erosion.

The bottom of the anvil stem I I8 rests against the top of a stack of annular washer-like members I26 contained within a cap block sleeve I28. The washers I26 transmit forces from the anvil stem 118 to the top of a pile (not shown) while the sleeve I28 contains the an nular members during such impact.

FIG. 6 illustrates schematically the hydraulic interconnections for operation of the hydraulic hammer described above. As shown in FIG. 6. there is provided a main hydraulic pump 130 which pumps hydraulic fluid from a reservoir 132 to a main hydraulic valve I34. The pump 130 in the preferred embodiment is capable of generating approximately 5,000 psi output at approximately 50 gallons per minute. This high pressure fluid is communicated via a pilot valve line I36 to pressure ports I38 of the downstrokc pilot valve 44 and of the latching pilot valve 46. The high pressure output from the main hydraulic pump I is also communicated through a constant high pressure line I40 to the lower pressure chamber 84 of the hydraulic hammer.

The high pressure output from the main hydraulic pump 130 is also connected to a pressure port I42 of the ram switching valve 40 and to the high pressure accumulators 48.

The ram switching valve has a switching port 144 which is connected alternately to the pressure port 142 and to a reservoir port 146, as the valve 40 is switched. The reservoir port 146, as indicated in FIG. 6, is connected to the reservoir 132. The switching port 144 of the ram switching valve 40 is connected through a switching line 148 to the upper pressure chamber 82 of the hydraulic hammer assembly.

The ram switching valve 40 is normally in the position shown in FIG. 6 with the switching port I44 connected to the reservoir port I46 and the pressure port I42 blocked. The ram switching valve 40 is actuated by application of pilot pressure via a ram switching valve pilot line 150 to a pilot input I52 on the valve. When the ram switching valve 40 is so switched. its switching port 144 becomes connected to the pressure port I42 while its reservoir port I46 becomes blocked. Thus, during operation of the ram switching valve 40. reservoir pressure and pump pressure are alternately applied to the switching line 148, and through this line to the upper pressure chamber 82.

The upstroke pilot valve 42 has a fluid input port 154 which receives high pressure fluid at selected times from either or both the downstroke pilot valve 44 and the latching pilot valve 46. The upstroke pilot valve 42 also contains a ram switching control port 156 connected via the ram switching valve pilot line 150 to the pilot port I52 of the ram switching valve 40. Further. the upstroke pilot valve 42 includes a reservoir port I58 which, as shown. is connected to the reservoir 132. The upstroke pilot valve, in its normal condition as shown in FIG. 6, has its fluid input port 154 blocked while its ram switching control port. which is eonnected via the ram switching valve pilot line to the ram switching valve pilot input port 152, is connected through the reservoir port 158 to the reservoir I32. When the upstroke pilot valve 42 is actuated, its ram switching control port 156 becomes connected to the fluid input port I56 while the reservoir port I58 becomes blocked. In this condition, provided that high pressure fluid is present at the fluid input port 154, such high pressure fluid will pass through the upstroke pilot valve 42 to the ram switching valve pilot line I and the pilot input pilot port I52 to actuate the ram switching valve 40. Actuation of the upstroke pilot valve 42 occurs by application of fluid pressure to a pilot input port I on the valve. This fluid pressure is received from an upstroke pilot line I62 which is connected to the lowermost pilot passageway I04 in the hammer assembly.

In its normal position, as shown in FIG. 6. the upstroke pilot valve 42 blocks the fluid input port I54 and connects the ram switching control port I56 to the reservoir port I58. When actuated, as by application of pilot pressure to the pilot input port 160, the upstroke pilot valve 42 blocks the reservoir port 158 and connects the input fluid port 154 to the ram switching control port 156. This switching takes place when the intermediate driving and control section 60h of the ram 60 moves up past the lowermost pilot passageway I04 and allows that passageway to be exposed to the high pressure of the lower pressure chamber 84.

The downstroke pilot valve 44 is provided with an output port I64 in addition to the pressure port 138. In its normal unactuated position, as shown in FIG. 6 the downstroke pilot valve 44 blocks the pressure port 138. When actuated however, the downstroke pilot valve 44 connects the pressure port 138 to the output port I64. As shown in FIG. 6, the output port 164 is connected to the fluid input port I54 of the upstroke pilot valve 42 while the pressure port 138 is connected to the pilot valve line 136.

The downstroke pilot valve 44 is actuated by application of high pressure fluid to a pilot input port 168 from a downstroke pilot line I70. The downstroke pilot line 170 is connected to the intermediate pilot passageway 102 in the hammer assembly; and it receives high pressure fluid for actuation for the downstroke pilot valve 44 whenever the ram 60 has risen sufficiently to bring its intermediate driving and control section 6012 above the pilot passageway I02 so as to expose that pilot pas sageway to the high pressure of the lower pressure chamber 84.

The latching pilot valve 46 also contains an output port 172 in addition to the pressure port 138. The output port 172 is connected, along with the output port I64 of the downstroke pilot valve 44, to the fluid input port I54 of the upstroke pilot valve 42. The pressure port I38 is connected to the pilot valve line I36, which in turn is connected to the high pressure output of the main hydraulic pump 130.

In its normal position as shown in FIG. 6, the latching pilot valve 46 has its pressure port I38 blocked. When the latching pilot valve 46 is actuated, its pressure port I38 is connected to the output port 172.

The latching pilot valve 46 is actuated by application of high pressure fluid to a pilot input port 176. This high pressure fluid is received from a latching pilot valve line 178 which in turn is connected to the uppermost pilot passageway 100 in the hammer assembly. It will be noted that the passageway I is located at the uppermost portion of the upper pressure chamber 82 and therefore pressure in the latching pilot valve I78 is unaffected by the position of the ram 60. Rather, the latching pilot valve line pressure depends strictly upon the pressure in the switching line I48.

As indicated in FIG. 6, the upper and lower bearing supply passageways 68 and 72 receive a continuous flow of high pressure fluid from the main hydraulic pump 130. This fluid drains off toward the upper end and lower end of the hammer assembly into upper and lower end chambers I80 and 182. These two chambers. as indicated previously, remain in open fluid communication via the axial bore 94. The upper end chamber 180 is connected via a drain line I84 and a pressure regulator I85, to the reservoir 132. A drain accumulator I86 is also connected to the drain line I84. The regulator 185 is set to maintain a minimal positive pressure within the end chambers I80 and I82. This drain accumulator may be mounted along with the accumulators 48 and 49 neaer the upper end of the hammer assembly. When the hammer assembly is to be used under water, the regulator 185 may be set to maintain pressure within the end chambers 180 and 182, equal to or vary slightly higher than the pressure of the surrounding water. This will prevent water from entering into the hammer assembly; and at the same time it will reduce stresses on the ring seal II2 of the anvil 114. As can be appreciated, the only element which moves and out from the hammer assembly during its operation is the anvil stem I18; and therefore the ring seal 112 is the only seal which must accommodate mechanical movement into and out from the system.

The operation of the hydraulic system described above will now be discussed in conjunction with FIG. 6-1] which show, respectively, the position ofthe ram 60 and the condition of the various valves 40, 42, 44 and 46 during each of these successive stages of operation.

Referring first to FIG. 6, where the ram 60 is shown as it begins upward movement within the outer casing, each of the various valves 40, 42, 44 and 46 is in its normal or un-actuated condition. Thus, the ram switching valve 40 connects the upper pressure chamber 82 through the switching line 148, to the reservoir I32. As a result, the upper pressure chamber 82 is at reservoir pressure. At the same time the lower reservoir chamber 84 is maintained at high pressure by its connection through the constant high pressure line I40 to the main hydraulic pump I30. Because of the higher pressure Within the lower pressure chamber 84 the ram 60 begins to move upwardly, causing the lower pressure chamber 84 to expand and the upper pressure chamber 82 to contract. The fluid which is swept out of the upper pressure chamber 82 by the upward movement of the ram 60 passes through the switching line I48 and the ram switching valve 40 to the reservoir I32. Also. during this upward ram movement, the ram itself displaces fluid from the upper end chamber I while it simultaneously evacuates the lower end chamber 182. However, because of the open and free fluid communication provided by the axial bore 94 between these two chamber ends, fluid may flow freely from the upper end chamber ISO to the lower end chamber 182. Since the upper end of the ram 60 is of smaller diameter than the lower end of the ram the amount of fluid displaced from the upper end chamber will not equal the increase in displacement of the lower end chamber I82 during ram movement. Accordingly fluid from the accumulator I86 passes in through the drain line 184 to make up for this difference.

Turning now to FIG. 7, it will be seen that when the ram 60 raises by an amount sufficient to bring the lowermost pilot passageway 104 into communication with the lower pressure chamber 84, the high pressure of that chamber is communicated via the upstroke pilot line I62 to the pilot input port I60 of the upstroke pilot valve 42. This actuates the valve 42 and brings its fluid input port I54 into communication with the ram switching control port I56. The upstroke pilot valve 42 at this point is in condition to actuate the ram switching valve 40. However no actuation takes place immediately upon this switching of the upstroke pilot valve 42 since its fluid input port 154 is initially blocked by means of the downstroke pilot valve 44 and the latching pilot valve 46.

It will be appreciated that during upward movement of the ram 60 within its casing, a downward reaction force is produced on the casing which, depending on the manner in which the hydraulic hammer assembly is supported. may cause the casing to shift downwardly slightly and thereby cause the anvil I I4 to raise slightly up into the lower end chamber I82.

The ram 60 continues its upward movement within the casing until, as shown in FIG. 8, the intermediate pilot passageway 102 comes into communication with the expanding lower pressure chamber 84. This causes high fluid pressure from that chamber to be communicated through the downstroke pilot line 170 to the pilot input port 168 of the downstroke pilot valve 44. As shown in FIG. 8, the downstroke pilot valve 44 thus becomes actuated so that its pressure port 138 is brought into communication with its output port 164. As a result, high pressure from the main hydraulic pump 130 is communicated through the pilot valve line 136, the downstroke pilot valve 44, the upstroke pilot valve 42, and the ram switching valve pilot line 150 to the pilot input port 152 of the ram switching valve 40. This causes actuation of the ram switching valve 40 and places its switching port 144 into communication with high pressure fluid passages from the main hydraulic pump 130. As a result high pressure fluid flows from the pump, through the switching line 148 and into the upper pressure chamber 82. This pressurizes the upper pressure chamber 82; and as a result, high pressure from that chamber is communicated through the uppermost pilot passageway 100 and through the latching pilot valve line 178 to the input port 176 of the latching pilot valve 46. This produces actuation of the latching pilot valve 46 and brings it to the condition shown in FIG. 8 with its pressure port 138 connected through its output port 172 to the fluid input port 174. It will be seen that at this point the operation of the latching pilot valve parallels that of the downstroke pilot valve 44 in that they both supply high pressure fluid through the upstroke pilot valve 42 to maintain the ram switching valve 40 in its actuated condition.

The application of high pressure fluid to the upper pressure chamber 82 also serves to reverse the net force application to the ram 60 thereby causing it to de celerate and eventually to begin a downward movement within the casing. This force reversal is obtained even though equal pressures exist in the two pressure chambers 82 to 84. The reason for this is that the upper pressure chamber 82 has a larger cross-sectional area than the lower pressure chamber 84. As can be seen in FIGS. 6-11 the ram diameter in the upper chamber 82 is smaller than the ram diameter in the lower chamber 84.

As a result of the above described force reversal, the ram 60 begins to move downwardly in the casing toward the anvil 114. During this downward movement the lower end of the ram displaces fluid out from the lower end chamber 182 and this fluid moves upwardly through the axial bore 94 into the upper end chamber 180. However, because the displacement of the ram into the lower end of chamber 182 is greater than the volume evacuated by the upper end of the ram an excess of fluid results. This excess fluid passes out through the drain line 184 and into the accumulator 186.

During the downward movement of the ram 60, as shown in FIG. 8, an upward reaction thrust is applied to the casing itself. Depending upon the magnitude of the forces involved, this thrust may be sufficient to cause the casing to move upwardly slightly during the downward ram movement. This slight upward casing movement is accomodated by a finite clearance d, between the head 116 of the anvil 114 and the bottom of the casing. Thus, the anvil is not pulled off from the pile which is to be hammered, but instead, the anvil remains on the pile while the casing itself may move upwardly. Actually, the downward movement of the ram causes a positive pressure to be maintained within the lower end chamber 182 which insures that the anvil 114 is continuously forced downwardly into firm positive contact with the cap block 62 so that an efficient transmission of energy from the ram to the pile will be achieved.

During downward movement of the ram 60, its transverse pilot passageway 96, which communicates via the axial bore 94 with the lower pressure in the end chambers 180 and 182, comes into communication with the intermediate pilot passageway 102, as illustrated in FIG. 9. Because of this, the high pressure previously applied through the downstroke pilot valve 44, via the downstroke pilot line 170, is removed and the down stroke pilot valve 44 reverts to its normal or unactuated condition as illustrated in FIG. 9. The deactuation of the downstroke pilot valve 44, however, has no effect upon the system because the latching pilot valve 46 remains actuated and insures a continued supply of pressurized fluid through the upstroke pilot valve 42 and the ram switching valve pilot line to maintain actuation of the ram switching valve 40.

As the ram 60 continues to move downwardly, the transverse pilot passageway 96 eventually comes into communication with the lower pilot passageway 104 of the casing and thereby removes high fluid pressure from the upstroke pilot line 162 and the pilot input port of the upstroke pilot valve 42. As a result, the upstroke pilot valve 42 becomes deactuated; and it reverts to its normal condition as shown in FIG. 10. This connects the ram switch valve pilot line 150 to the reservoir 132 and thereby removes pressure from the pilot input port 152 of the ram switching valve 40. As a result, the ram switching valve reverts to its unactuated condition as shown in FIG. 10 and causes the switching line 148 to communicate with the reservoir 132 and causes a net reversal of forces on the ram 60.

The above described switching action, to produce force reversal on the ram 60, is timed to occur either just before, just after or just when the ram strikes the anvil. The timing of this switching can be controlled by selection of the longitudinal position of the lowermost pilot passageway 104 along the casing. Also, various hydraulic delay arrangements can be interposed along the upstroke pilot line 162 for controlling the timing of deactuation of the upstroke pilot valve 42. The timing of force reversal on the ram 60 should be such as to insure that maximum momentum of the ram is transferred to the anvil 114 at the moment of impact without however, allowing the ram to cause the anvil to bottom on the casing.

As shown in FIG. 11, the ram 60, upon striking the anvil 114, forces it downwardly thereby to drive the pile or other element engaged by the anvil. During this downward movement, the stem 118 of the anvil moves downwardly through the ring seal 112 and out from the bottom of the casing.

When the downward momentum of the ram has been dissipated through the above described driving action on the anvil 1 14, the pressure within the lower pressure chamber 84 becomes sufficient to raise the ram in an upward direction; and the above described cycle is repeated.

It will be appreciated from the foregoing that while relatively high hydraulic pressures are maintained in the upper and lower pressure chambers 82 and 84, any leakage of hydraulic fluid past the upper and lower ram seals 74 and 78 is accomodated in the upper and lower chambers and 182. Any excess fluid thus accumulated may readily be expelled via the drain line 184 to the accumulator 186 or to the reservoir 132.

It will further be appreciated that only a single mov ing element, i.e., the anvil stem 118 requires a seal for isolating the interior of the hammer assembly from outside conditions. By maintaining the pressure within the upper and lower end chambers 180 and I82 at close to the pressure of the surrounding ambient. stresses on the ring seal 2 are minimized. Thus, when the hammer assembly is operated at great water depths, the pressure within the end chambers 180 and 182 can be maintained approximately equal to or slightly greater than the pressure of the surrounding water. In such case the ring seal 112 is enabled to maintain isolation of the interior of the hammer assembly from the surrounding water with minimal leakage. It will further be appreciated that by causing the ram to impact the anvil within the hammer assembly casing the need for sealing the relatively long stroke ram from the external ambient is eliminated. Instead, only the anvil stern, which moves a relatively small amount, need be sealed from the exterior of the assembly.

It will further be appreciated that the construction of the hydraulic hammer of the present invention, which utilizes a three piece casing held together by tie rods, is easily assembled and disassembled and facilitate the replacement and reconditioning of worn or broken parts. Moreover, the rating of the hammer assembly can readily be changed simply by substituting a different ram of the same exterior dimension as the ram 60 but having a different size axial bore 94. Alternatively, internal sleeves may be provided inside the axial bore 94 to change the effective mass of the ram.

Having thus described the invention with particular reference to the preferred form thereof, it will be obvious to those skilled in the art to which the invention pertains, after understanding the invention, that various changes and modifications may be made therein without departing from the spirit and scope of the invention, as defined by the claims appended hereto.

We claim:

1. in a hydraulic hammer, the combination of a closed casing having first, second and third bores. a ram reciprocally movable in said casing bores and having a central driving region slideable in said second bore and first and second smaller diameter end regions at each side of the central driving region and slideable within the first and third bores of said casing and forming first and second end chambers therein, an anvil having a blow receiving head in said first end chamber and located in the path of ram movement and further having a stem projecting through and closely fitted and sealed in an opening at one end of said casing in a manner permitting limited longitudinal movement of said stem in the direction of ram movement, fluid drive means operative to act on said central driving region for driving said ram reciprocally in said casing to impact against the blow receiving head of said anvil and pressure maintaining means for maintaining a continuous positive fluid pressure within said first and second end chambers to hold said anvil toward said one end with its stem projecting from said one end and in contact with an element to be driven, even during uplift reactions on said casing caused by the driving of said ram, said pressure maintaining means comprising means for supplying a pressurized fluid within said first and second end chambers and a first fluid passageway means connecting said end chambers.

2. A hydraulic hammer according to claim 1 wherein said anvil has a convexly shaped blow receiving head and wherein said ram has a correspondingly concavely shaped bottom end for impacting said anvil.

3. A hydraulic hammer according to claim 1 wherein said separate anvil bearing means are interposed between said casing and said anvil at both said blow receiving head and said stem.

4. A hydraulic hammer according to claim 3 wherein said anvil is formed with fluid passageway extending between its blow receiving head and its periphery between said anvil bearing means.

5. In a hydraulic hammer, the combination of a closed casing, a ram reciprocally moveable in said casing, an anvil having a blow receiving head in said casing and located in the path of ram movement and further having a stem projecting through and closely fitted and sealed in an opening at one end of said casing in a manner permitting limited longitudinal movement of said stem in the direction of ram movement, first means for driving said ram in said casing to impact against the blow receiving head of said anvil and second means for maintaining a continuous positive pressure within said casing between said ram and anvil to bias said anvil with its stem projecting from said opening and in contact with an element to be driven, even during uplift reactions on said casing caused by the driving of said ram, said second means for maintaining a continuous positive pressure comprising fluid passageway means extending from within the casing between said anvil and ram to an external accumulator.

6. A hydraulic hammer according to claim 5 wherein said fluid passageway is formed in part by a longitudinal bore extending through the length of said ram.

7. A pile drive hammer comprising a casing, a ram fitted inside and enclosed by said casing for longitudinal movement therein, an anvil within said casing in the path of movement of the ram for receiving blows from the ram, said ram defining, within the interior of said casing, spaces which change in volume with ram movement inside said casing, means maintaining said spaces filled with liquid, means for moving said ram inside said casing and means maintaining the opposite ends of said casing in open liquid communication with each other whereby movements and hammering action of said ram occurs while said ram is submersed in said liquid, said means for moving said ram inside said casing compris ing a larger diameter region of said ram fitted into a corresponding large diameter bore of said casing and dividing said large diameter bore of said casing into a pair of variable size pressure chambers and wherein said means for moving said ram includes means for controlling pressurized fluid flow to and from said pressure chambers.

8. A pile driving hammer according to claim 7 wherein said pressure chambers are pressure isolated from said ends of said casing by means of sliding pressure seals between said casing and said ram at each end of said pressure chambers.

9. A pile driving hammer according to claim 7 wherein said ram is supported for free axial movement in said casing by means of hydrostatic bearings located between said sliding pressure seals and the ends of said casing.

10. A pile driving hammer according to claim 7 wherein said means maintaining said first and third bores in open liquid communication with each other comprises a fluid passageway formed in and extending through the length of said ram.

11. A fluid actuated hammer system comprising a casing, a ram mounted for reciprocal movement within the casing, an anvil having a portion thereof located within said casing in the path of movement of said ram to be struck by said ram without the casing, said anvil having a portion thereof extending out from said casing, means maintaining a supply of liquid at a positive pressure within said casing in the regions thereof displaced by movement of said ram and means maintaining said regions in open fluid communication, hydraulic actuator means within said casing and connected to produce movement of said ram in said casing, said hydraulic actuator means including a variable size chamber which changes size in response to movements of fluid into and out from said chamber and sliding pressure seal means isolating said variable size chamber from said regions.

12. A fluid actuated hammer according to claim 11 wherein said means maintaining said regions in open fluid communication a fluid passageway formed in and extending through the length of said ram.

13. A fluid actuated hammer according to claim 11 wherein said portion of said anvil extending out from said casing is sealed with respect to said casing by means of sliding pressure seal means.

14. A fluid actuated hammer according to claim 11 wherein said variable size chamber is formed in part by piston means moveable with said ram.

15. A fluid actuated hammer according to claim 11 wherein said hydraulic actuator means includes pres sure actuated switching valve means arranged to control fluid flow to and from said variable size chamber and actuation means for actuating said switching valve means, said actuation means comprising a fluid connection to said casing at a location to be exposed to said variable size chamber when said chamber attains a predetermined size.

16. A differential acting fluid driven hammer comprising a casing having an enlarged diameter central bore and a pair of smaller diameter bores at each end of the enlarged diameter bore, a piston ram having an enlarged central region closely fitted into the central bore of the casing, said ram further having first and second regions closely fitted into the smaller diameter bores of said casing and forming first and second end chambers therein, said piston ram being reciprocally moveable in said casing, the enlarged central region of said ram dividing said central bore of said easing into first and second pressure chambers, an anvil having a head positioned in said first end chamber of the casing in the path of movement of said piston ram to be struck thereby, and a stem extending out from the end of said casing proximate said first bore. sliding pressure seal means between said casing and said ram at each end of said first and second pressure chambers respectively and further sliding pressure seal means between said casing and said anvil, said ram being formed with a passageway extending longitudinally between its ends and placing said first and second end chambers in open fluid communication with each other, and means for controlling the flow of pressurized fluid into and out from said pressure chambers to control piston ram movements within said casing.

17. A differential acting fluid hammer according to claim 16 wherein said smaller diameter bores of said casing are of diiferent diameters.

18. A differential acting fluid hammer according to claim 16 wherein said casing is formed of an assembly of segments in stacked array and held together with tension members extending along the outside of the segments.

19. A differential acting fluid hammer according to claim 18 wherein said means for controlling the flow of pressurized fluid includes hydraulic valve means and means for actuating said valve means in accordance with the position of said piston ram in said casing.

20. A differential acting fluid hammer according to claim 19 wherein said casing is formed with pilot pressure ports which are exposed to different pressures within said casing as the enlarged central portion of said ram moves past said ports and means responsive to changes in pressure at said ports to actuate said hydraulic valve means.

21. A pile driving hammer according to claim 7 wherein said first bore is of intermediate diameter and said third bore is of small diameter relative to the second bore and wherein said ram further comprises first and second end regions slideable within said first and second bores. 

1. In a hydraulic hammer, the combination of a closed casing having first, second and third bores, a ram reciprocally movable in said casing bores and having a central driving region slideable in said second bore and first and second smaller diameter end regions at each side of the central driving region and slideable within the first and third bores of said casing and forming first and second end chambers therein, an anvil having a blow receiving head in said first end chamber and located in the path of ram movement and further having a stem projecting through and closely fitted and sealed in an opening at one end of said casing in a manner permitting limited longitudinal movement of said stem in the direction of ram movement, fluid drive means operative to act on said central driving region for driving said ram reciprocally in said casing to impact against the blow receiving head of said anvil and pressure maintaining means for maintaining a continuous positive fluid pressure within said first and second end chambers to hold said anvil toward said one end with its stem projecting from said one end and in contact with an element to be driven, even during uplift reactions on said casing caused by the driving of said ram, said pressure maintaining means comprising means for supplying a pressurized fluid within said first and second end chambers and a first fluid passageway means connecting said end chambers.
 2. A hydraulic hammer according to claim 1 wherein said anvil has a convexly shaped blow receiving head and wherein said ram has a correspondingly concavely shaped bottom end for impacting said anvil.
 3. A hydraulic hammer according to claim 1 wherein said separate anvil bearing means are interposed between said casing and said anvil at both said blow receiving head and said stem.
 4. A hydraulic hammer according to claim 3 wherein said anvil is formed with fluid passageway extending between its blow receiving head and its periphery between said anvil bearing means.
 5. In a hydraulic hammer, the combination of a closed casing, a ram reciprocally moveable in said casing, an anvil having a blow receiving head in said casinG and located in the path of ram movement and further having a stem projecting through and closely fitted and sealed in an opening at one end of said casing in a manner permitting limited longitudinal movement of said stem in the direction of ram movement, first means for driving said ram in said casing to impact against the blow receiving head of said anvil and second means for maintaining a continuous positive pressure within said casing between said ram and anvil to bias said anvil with its stem projecting from said opening and in contact with an element to be driven, even during uplift reactions on said casing caused by the driving of said ram, said second means for maintaining a continuous positive pressure comprising fluid passageway means extending from within the casing between said anvil and ram to an external accumulator.
 6. A hydraulic hammer according to claim 5 wherein said fluid passageway is formed in part by a longitudinal bore extending through the length of said ram.
 7. A pile drive hammer comprising a casing, a ram fitted inside and enclosed by said casing for longitudinal movement therein, an anvil within said casing in the path of movement of the ram for receiving blows from the ram, said ram defining, within the interior of said casing, spaces which change in volume with ram movement inside said casing, means maintaining said spaces filled with liquid, means for moving said ram inside said casing and means maintaining the opposite ends of said casing in open liquid communication with each other whereby movements and hammering action of said ram occurs while said ram is submersed in said liquid, said means for moving said ram inside said casing comprising a larger diameter region of said ram fitted into a corresponding large diameter bore of said casing and dividing said large diameter bore of said casing into a pair of variable size pressure chambers and wherein said means for moving said ram includes means for controlling pressurized fluid flow to and from said pressure chambers.
 8. A pile driving hammer according to claim 7 wherein said pressure chambers are pressure isolated from said ends of said casing by means of sliding pressure seals between said casing and said ram at each end of said pressure chambers.
 9. A pile driving hammer according to claim 7 wherein said ram is supported for free axial movement in said casing by means of hydrostatic bearings located between said sliding pressure seals and the ends of said casing.
 10. A pile driving hammer according to claim 7 wherein said means maintaining said first and third bores in open liquid communication with each other comprises a fluid passageway formed in and extending through the length of said ram.
 11. A fluid actuated hammer system comprising a casing, a ram mounted for reciprocal movement within the casing, an anvil having a portion thereof located within said casing in the path of movement of said ram to be struck by said ram without the casing, said anvil having a portion thereof extending out from said casing, means maintaining a supply of liquid at a positive pressure within said casing in the regions thereof displaced by movement of said ram and means maintaining said regions in open fluid communication, hydraulic actuator means within said casing and connected to produce movement of said ram in said casing, said hydraulic actuator means including a variable size chamber which changes size in response to movements of fluid into and out from said chamber and sliding pressure seal means isolating said variable size chamber from said regions.
 12. A fluid actuated hammer according to claim 11 wherein said means maintaining said regions in open fluid communication a fluid passageway formed in and extending through the length of said ram.
 13. A fluid actuated hammer according to claim 11 wherein said portion of said anvil extending out from said casing is sealed with respect to said casing by means of sliding pressure seal means.
 14. A fluid actuated hammer According to claim 11 wherein said variable size chamber is formed in part by piston means moveable with said ram.
 15. A fluid actuated hammer according to claim 11 wherein said hydraulic actuator means includes pressure actuated switching valve means arranged to control fluid flow to and from said variable size chamber and actuation means for actuating said switching valve means, said actuation means comprising a fluid connection to said casing at a location to be exposed to said variable size chamber when said chamber attains a predetermined size.
 16. A differential acting fluid driven hammer comprising a casing having an enlarged diameter central bore and a pair of smaller diameter bores at each end of the enlarged diameter bore, a piston ram having an enlarged central region closely fitted into the central bore of the casing, said ram further having first and second regions closely fitted into the smaller diameter bores of said casing and forming first and second end chambers therein, said piston ram being reciprocally moveable in said casing, the enlarged central region of said ram dividing said central bore of said casing into first and second pressure chambers, an anvil having a head positioned in said first end chamber of the casing in the path of movement of said piston ram to be struck thereby, and a stem extending out from the end of said casing proximate said first bore, sliding pressure seal means between said casing and said ram at each end of said first and second pressure chambers respectively and further sliding pressure seal means between said casing and said anvil, said ram being formed with a passageway extending longitudinally between its ends and placing said first and second end chambers in open fluid communication with each other, and means for controlling the flow of pressurized fluid into and out from said pressure chambers to control piston ram movements within said casing.
 17. A differential acting fluid hammer according to claim 16 wherein said smaller diameter bores of said casing are of different diameters.
 18. A differential acting fluid hammer according to claim 16 wherein said casing is formed of an assembly of segments in stacked array and held together with tension members extending along the outside of the segments.
 19. A differential acting fluid hammer according to claim 18 wherein said means for controlling the flow of pressurized fluid includes hydraulic valve means and means for actuating said valve means in accordance with the position of said piston ram in said casing.
 20. A differential acting fluid hammer according to claim 19 wherein said casing is formed with pilot pressure ports which are exposed to different pressures within said casing as the enlarged central portion of said ram moves past said ports and means responsive to changes in pressure at said ports to actuate said hydraulic valve means.
 21. A pile driving hammer according to claim 7 wherein said first bore is of intermediate diameter and said third bore is of small diameter relative to the second bore and wherein said ram further comprises first and second end regions slideable within said first and second bores. 